Self-adjusting wrench for nuts or like polygonal objects



Och 1951 M. F. STELLINGER 2,570,991

SELF-ADJUSTING WRENCH FOR NUTS OR LIKE POLYGONAL OBJECTS Filed Jigne 10, 1949 W, Mam/FM Patented Oct. 9, 1951 SELF-ADJUSTING WitENCH FOR NUTS R LIKE POLYGONAL OBJECTS Mogens Fin 'Stellinger, Copenhagen, Denmark,

assignor 'to The Cromna Company, Copenhagen, Denmark, a firm Application June 10, 1949, Serial No. 98,188 In Great Britain December 16, 194 8 a Y 3Claims. (Cl. s1-91) 1 fThis invention relates to wrenches and. is, more specifically, concerned with wrenches of the type disclosed in the co-pending patent application Serial Nd. 786,289 by s. o. Mortensen'j The wrench in accordancewiththe said'patent 'apjplication comprises a pair of opposed jawsof .which' one is rigidly connected with the shank or handle of the wrench, whilst the other jaw is substantially hook-shaped and pivotally connected with the handle in such a manner that the jaws are-squeezed against an object engaged between them when the handle is actuated to turn such object, one of the jaws being provided with an approximately semi-cylindrical jaw member pivotally mounted in an arcuate recess in the jaw in question in such a manner that the flat face of such member constitutes the gripping face of saidjaw. V V

As a result of experiments made, it has been found that the best construction isthat in which the semi-cylindrical jaw member is mounted in the handle of the wrench. This construction, .however, involves certainpractical problems the solution of which constitutes the object of the present invention. I I

Another object is to provide such construction of the wrench in question as to ensure that the gripping faceof the semi-cylindrical jaw member will always automatically facially engage a nut or the like to be turned by means of the wrench. Still another objectis to generally improve the wrench disclosed in the aforesaid patent application.

The invention will now be described in detail with reference to the accompanying drawing in which h Fig. 1 is a side-view of a' wrench in accordance with the invention,

Fig. 2 is a section taken along the line II-.II in Fig. 1, and Fig. 3 illustrates the 'tion of the wrench.

In the drawing, l is the handle of the wrench, 2 a bearing for an arcuately sliding jaw 9, the bearing being integral with the handle, and 5 a pivotable hook-shaped jaw which, by means of a pin 4 is hingedly connected with the handle I, which latter is formed with a recess I6 engaged by an approximately circular web [5 on the jaw ,5. A coil spring I1 is provided in the recess I5 and acts to urge the pivotable jaw 5 towards the arcuately sliding jaw 9. The latter is formed by an approximately semi-cylindrical member and is mounted for pivoting movement in its bearing geometrical determinaof span of the wrench.

ing 2.

relative to the bearing 2 a set screw I2 is in- 2 in such a manner that its fiat face 3 constitutes the gripping facelof the jaw. The grippingjface -of the pivotable jaw is denoted by 6 and this jaw is furthermore provided with a face '1 constituting an angle of 120? with the'gripping 'faceB "andacting as an abutment for a nut 8 engaged in the wrench.

The jaw 9 is retained'in its'bearing bymeans ferential portion of the jaw and engaged by a corresponding feather I0 provided in the'bear- In order to limit rotation of the jaw 9 serted from the recess I6 to engage a smaller groove 13, which is formed in the bottom of the dove-tailgrocve II and extends over a certain angle only of the circumferential face of the jaw 9. The length of the groove I3 is such as to permit the jaw to adjust itself freely to engage the side faceof any nut of a size within the'range It will be appreciated that, if the grippingface 3 of the jaw 9 shall apply itself automatically to the side face of the nut 8 when the handle Iis actuated in the direction of the arrow C to squeeze the jaws of the wrench together about the nut,

.the lower face of the nut must, in the position defined by the faces 6 and I, engage the gripping face 3 so as to be intersected by a planeof symmetry l4 perpendicular to said lower face and applied.

It will equally be appreciated that another re- ;quirement to be fulfilled in order to ensureefw fective operation of the wrench is that a line 20 drawn from the axis of the pin 4 to the corner sible at right angles to the gripping face 6, be-

nut to rotate will extend in the direction of said line and, therefore, will have a considerable com- "ponent in the direction of the gripping face 6 if the aforesaid angle is substantially above 90, whereby the gripping face 6 may be urged to slip upon the nut 8 instead of engaging the same firmly. The ideal would be if the angle between the face 6 and the line Zll were 90, but this is impracticable and is furthermore practically incompatible with the aforesaid requirement of the engagement between the nut 8 and the gripping face 3, as will become apparentfrom the followe s then the axis of the pin 4 would be situated upon a line 20, e. g. at the point 4. Thi would result, when turning the jaw 5 through a definite angle to vary the span of the wrench, in only a very small change of the distance between the faces 3 and B, and in a relatively great lateral displacement of the nut 8 with respect to the line l4. If under these'conditions the requirement is maintained that the nut must engage the face 3 on either side of the line l4, the wrench would afford a very small range of span. With a de finite range of span a reduction of the lateral displacement of the nut relative to the line I4 can only be attained by reducing the distance A between the axis of the jaw 9 and the axis of the pin 4. This distance must, however, always be greater than the sum of the radius of the web I5 and the radius of the arcuate recess forming the bearing for the jaw 9. These radii are both determined by practical requirements and with a viewto the necessaryjstrength of the wrench.

The present invention, however, affords the possibility of substantially reducing the distanceA other in such a manner that a satisfactory result I is obtained. The requirements capitulated, as follows:

1. The wrench must possess a reasonable range of span.

2. A nut of any size within the range of span of the wrench must; when'engaged in the wrench, make contact with the gripping faceof the jaw 9 on both sides of the pivot axis thereof.

3. The angle between the face 6 and the'line 29 must be as near as is possible to 90.

Practical experiments have shown that these requirements can all be reasonably fulfilled when the ratio between the sizes of the largest and the smallest nut to which the wrench is applicable is are, briefly reabout l zl and the ratio between the distance A and the distance between opposed faces of the largest nut does not exceed about 1 :1. It should be noted that, when determining the range of span of the wrench, a minor allowance should be made for enabling the wrench to span the largest nut at diametrically opposed corners thereof, in order to enable it to operate likea ratchet wrench. This implies that the ratio between the largest and the smallest sp'an'of the wrench is not the same as the ratio between the sizes of the largest and the smallest nut, viz. l zl approximately; but as far as hexagonal nuts are concerned, approximately /3;1 r about 1% :1. The maximum ratio betweenthe measure A. and the largest span of ,the wrench. should accordingly beabout 1 /3=% /3:l or approximately 1.3:l. If under these conditions the smallest .permissible distancebetweenthe axis of .the jaw 9 and the nearest edge of the nut engaging the gripping 5 areof importanceto the geometrical deter-v 4 mination thereof. The principle of effecting the construction may briefly be explained as follows: The nut 8 is supposed to be situated upon the gripping face 3 of the jaw 9 in the position which is to be assumed when the nut is engaged in the wrench, i. e. when the faces 6 and l engage corresponding faces, of the nut. Assuming that the nut is of the smallest size to which the wrench is applicable, the nut will have its centre at a certain distance to the left of the line 14 in such a manner thatrthe distance Di from the line [4 to the lower right corner of the nut 8 is the smallest permissible. The nut is now supposed to increase in size, whilst the cradle 9 is held immovable. When hereby the nut is caused to constantly engage the faces 6 and 'l of the jaw 5, it will be laterally displaced towards the right at the same time as the axis of the pin 4 will be displaced along a circle or arc 2| having its center on the axis of the cradle 9 and a radius equal to A. When the nut has attained its maximum size, which is denoted by 8, the face 6 will have assumed the position 6. and the distance between 'the line l4 and the lower left corner of the nut 8' will be D2. The distances DI and D2 may theoretically be freely" selected, but practically-they are selected in such a manner as to be approximately equal and just enough to ensure thedesired automatic adjustment of the jaw 9.

The are of the circle 2! through which theaxis of the pin 4 is displaced, is now determined in the following manner.

The face 6 remaining parallel to itself during the Whole movement, the jaw-5 will be displaced in such a manner that all points thereof are displaced parallelly through equal distances. The extent and direction of this displacement are determined by the length L of a line drawn from the upper right corner of the nut 8 to the upper right corner of the nut 8. Thus thislength of line indicates the length and direction of a chord to the arc of the circle'2l, through which the axis of the pin 4 is displaced. Therefore, a line 22 is drawn through the point of intersection between the line l4 and the'grippin'g face of the jaw 9 at right angles to the extension of the'line'L, and subsequently lines23 and 24 are drawn on either side of the lines 22 at a distance of L/2 therefrom. The points of intersection 4a and 4b between the lines 23 and 24, respectively, and the circle 2| define the are along which the axis of the pin 4 is displaced when the size of the nut engaged in the wrench varies from minimum to maximum. A line 25 drawn from'the point 4a at right angles to the face 6 represents the distance between this face'and the axis of the pin be about l l :times the corresponding measure blof the nut H I Ashereinbefore stated, allowance should be ,made for permitting.. the wrench to. span diametrically oppqsed edges of .the. nut 8 This allowance is determined in the following manner:

.A ar 2 havine ispen er n th l wer i h corner of thenut fl. is drawn from thefupper left corner of the nut, and a' tangent 6" to this ar r n. p ra l l o th line b eguent y the point lc of the circle 2| whose distance from the line 6 is equal to the length of the line 25, is marked upon the circle, and the angle a. of the arc la-4c is then the angle through which the jaw 5 must be capable of moving relative to the handle I. This angular movement is defined by abutments 21 and 28 on the handle of the wrench (Fig. 1). These abutments thus prevent the wrench from being used with nuts to which it is not intended to be applied.

I claim:

1. A wrench comprising a handle, an arcuately slidable jaw associated with said handle, a substantially hook-shaped jaw pivotably connected with said handle and having a workpiece-engaging portion which forms an angular notch, said portion including a substantially straight gripping face confronting said arcuately slidable jaw, an arcuate recess in said handle, a substantially semi-cylindrical member forming said arcuately slidable jaw and having a substantially straight edge face and being mounted in said arcuate recess for free arcuately sliding movement around an axis lying substantially in said straight edge face so as to be positioned, by engaging one parallel side of said workpiece, with its straight edge face parallel to said gripping face of said hook-shaped jaw when the latter engages an opposite parallel side of said workpiece, and means on said hook-shaped jaw and handle for limiting pivotal movement therebetween, so that any polygonal parallel-sided workpieces, between maximum and minimum sizes to be en- 6 gaged in the wrench, will have said one parallel side engaging said straight edge face on both sides of said axis, when said workpiece abuts an interior corner of said angular notch.

2. A wrench as in claim 1 in which said semicylindrical jaw member has an undercut circumferential groove engaged by a corresponding feather in said arcuate recess to retain said jaw member therein.

3. A wrench as in claim 1 in which said means for limiting pivotal movement between said hookshaped jaw and said handle are such as to insure a ratio between the largest and the smallest span of the wrench of approximately /:1 and a ratio between the distance from the axis of said semi-cylindrical arcuately sliding jaw to the pivot axis of said hook-shaped jaw and said largest span, not exceeding about /3:1.

MOGENS FIN zSTELLINGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

